فروشگاه کوچک (پروژهٔ پایانی)

import json, queue, threading
from dataclasses import dataclass, asdict

@dataclass
class Product:
    sku: str
    name: str
    price: float

DISCOUNTS = {"normal": lambda a: a, "student": lambda a: a * 0.7}

class Cart:
    def __init__(self):
        self.items = []
    def add(self, product, qty=1):
        if qty <= 0:
            raise ValueError("تعداد باید مثبت باشد.")
        self.items.append({"product": product, "qty": qty})
    def total(self, kind="normal"):
        raw = sum(i["product"].price * i["qty"] for i in self.items)
        try:
            return DISCOUNTS[kind](raw)
        except KeyError:
            raise ValueError(f"تخفیف ناشناخته: {kind}")

def save(products, path):
    with open(path, "w", encoding="utf-8") as f:
        json.dump([asdict(p) for p in products], f, ensure_ascii=False, indent=2)

cart = Cart()
cart.add(Product("b1", "کتاب", 12000), 2)
print(cart.total("student"))  # 16800.0